In contrast, Clinton’s challengers for the Democratic presidential nomination have been emotionally accessible. Barack Obama wrote about his absent father in Dreams From My Father and about quarreling with his wife in The Audacity of Hope.

John Edwards, former senator from North Carolina, is the star of a long-running, heart-rending family drama: he lost a son in a car accident and has a wife with incurable cancer and he discusses all of it with seeming ease.

In contrast, Clinton has meted out her inner life one teaspoon at a time: a suggestive line in an interview here, a hearty laugh there.

So on Monday, when she choked up during an appearance at a New Hampshire coffee shop, making a nakedly emotional plea for her candidacy, Clinton prompted one of the most fiercely debated moments of the presidential campaign to date.

“If she is breaking down now, before winning her party’s nomination, then how would she act under pressure as President?” Mark Mayfield, 52, a sales manager in Nashville and a supporter of Obama, wrote in a post on nytimes.com.

As if in reply, Katha Pollitt wrote on thenation.com that the spectacle of Clinton misting over brought up “the oldest, dumbest canard about women: they’re too emotional to hold power”.

Americans from across the political spectrum played and replayed the clip, pausing on every flicker of expression on Clinton’s face, asking questions like: After a political lifetime of keeping her emotions secret, why was Clinton finally letting her guard down? Was it a spontaneous outburst or a calculated show?

Meanwhile, in a telephone interview, Marianne Pernold Young, 64, the photographer whose question prompted Clinton’s choked-up response at a coffee for undecided New Hampshire voters, said she was stuck between Clinton and Obama.

Young sounded mystified over the reaction to her question. After all, her original inquiry to Clinton had been a fairly light one. “My question is personal: How do you do it?” she had asked Clinton. “Who does your hair?”